[Stoves] Understanding TLUDs, MPF and more. (was Re: Bangladesh TLUD )

[Crispin Pemberton-Pigott]

Dear Paul

You are going to have to give up on certain preconceptions and look at stoves and how they work.

TLUD is an abbreviation for an ignition and air flow direction. That's all. I fully realise why would you like to appropriate it for a single type of device, but that would leave the rest of the nomenclature with a gap. There is a practical need for a vocabulary and BLDD and ELCD (end-lit cross draft) are reasonable abbreviations to use in formal discussions. You were once on favour of using TLUD pyrolytic gasifier. I think that is a great name. What happened?

>2.  Referring to burning charcoal, tell me about lighting of cold CHARCOAL on the top.

This is routinely done in charcoal stoves where the limitation of smoke is desired. A device for enhancing the speed of top lighting charcoal is being promoted national in Laos right now. They found it is use more than twice per day on average. It greatly speeds ignition on top and limits smoke production significantly both during ignition and immediately afterwards.

>The reality is that charcoal fires are lit at the bottom (bottom burning) and the when the pyrolytic front reaches the bottom of a batch TLUD operation, the fire (the glowing char) is at the bottom.

Some people light their charcoal from below. Lots of people don't. You are correct that when a TLUD pyrolytic gasifier has finished there is a contained of glowing charcoal lit at the bottom only. That doesn't affect how people in Java and Laos top-light their charcoal.

>So where do you get this stuff about a descending "fire front" in charcoal fires?

For heaven's sake Paul look at some devices that don't work the way a TLUD pyrolytic device does. You are repeatedly telling me how things don't work or can't work. It's a big planet.
>Air  coming in on the top does burn some char, but that is hardly the way that a charcoal fire works.

A TLUD charcoal fire is lit on top and the air comes through the fuel from below. This is not a difficult concept. It is a TLUD charcoal burner. It is not a pyrolyser, it is a gasifier. In the case of a Keren Supra Nova it has preheated secondary air introduced above the burning fuel (which is burning in an air-starved condition) to complete the combustion of the gases - mostly CO.

Here is a TLUD Keren Supra Nova charcoal gasifier with preheated secondary air, that burns with a descending char combustion zone. It is based on the Thai Bucket stove which was copied locally as the Keren Supra. This version removes the insulation between the clay and the metal container using the space as a secondary air preheater. It is cheaper than and outperforms the Keren Supra, already an' improve cooking stove'.

[cid:image003.jpg at 01D37408.967C8660]

This stove can also be operated as a TLUD char making stove fueled with wood pellets. These char pellets can be recovered and used later as fuel in the charcoal burning TLUD mode, that is top lit, with a descending fire zone instead of a descending pyrolysis zone.

Charcoal stoves should always be lit on top. It burns cleaner and longer. Using a Lighting Cone speeds the ignition considerably, which is why SNV is promoting them in Laos.

As I understand it, you want to have this stove defined as a TLUD when it is pyrolysing the pellets to make char, but when it is operating as a TLUD burning that char, it is 'something else'. That is why I encourage you to describe your stoves as TLUD pyrolysing gasifiers or TLUD pyrolysers. There are other devices that all of the time, or part of the time, operate in TLUD mode.

Regards
Crispin

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